Designation: D 2256 – 02
Standard Test Method for
Tensile Properties of Yarns by the Single-Strand Method1
This standard is issued under the fixed designation D 2256; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method covers the determination of tensile
properties of monofilament, multifilament, and spun yarns,
either single, plied, or cabled with the exception of yarns that
stretch more than 5.0 % when tension is increased from 0.05 to
1.0 cN/tex (0.5 to 1.0 gf/tex).
1.2 This test method covers the measurement of breaking
force and elongation of yarns and includes directions for the
calculation of breaking tenacity, initial modulus, chord modulus, and breaking toughness.
1.2.1 Options are included for the testing of specimens in:
(A) straight, (B) knotted, and (C) looped form.
1.2.2 Conditions of test are included for the testing of
specimens that are: (1) conditioned air, (2) wet, not immersed,
(3) wet, immersed, (4) oven-dried, (5) exposed to elevated
temperature, or (6) exposed to low temperature.
D 1578 Test Method for Breaking Strength of Yarn in Skein
Form2
D 1776 Practice for Conditioning and Testing Textiles2
D 2258 Practice for Sampling Yarn for Testing2
D 2904 Practice for Interlaboratory Testing of a Textile Test
Method that Produces Normally Distributed Data2
D 2906 Practice for Statements on Precision and Bias for
Textiles2
D 3822 Test Method for Tensile Properties of Single Textile
Fibers3
D 4848 Terminology of Force, Deformation and Related
Properties of Textiles3
D 4849 Terminology Relating to Yarns and Fibers3
E 178 Practice for Dealing with Outlying Observations4
3. Terminology
3.1 Definitions:
3.1.1 Refer to Terminology D 4848 for definitions of the
following terms used in this standard: breaking force, breaking
strength, breaking tenacity, breaking toughness, chord modulus, elongation, elongation at break, elongation at rupture,
initial modulus, knot-breaking force, knot breaking strength,
linear density, loop breaking force, loop-breaking strength,
single-strand breaking force, single-strand breaking strength,
strength and tenacity.
3.1.2 Refer to Terminology D 123 and Terminology D 4849
and for definitions of other terms used in this standard.
NOTE 1—Special methods for testing yarns made from specific fibers;
namely, glass, flax, hemp, ramie, and kraft paper and for specific products;
namely, tire cords and rope, have been published: Test Method D 885, and
Specification D 578.
NOTE 2—For directions covering the determination of breaking force of
yarn by the skein method refer to Test Method D 1578.
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
4. Summary of Test Method
4.1 Single-strand yarn specimens are broken on a tension
testing machine at a predetermined elongation rate and the
breaking force and the elongation at break are determined.
Elongation at a specified force or the force or tenacity at a
specified elongation may also be obtained. Breaking force,
breaking tenacity, elongation, initial and chord modulus, and
breaking toughness of the test specimen, in terms of linear
density, may be calculated from machine scales, dials, recording charts, or by an interfaced computer.
4.2 This test method offers the following three physical
configurations of the specimen:
4.2.1 Configuration A, straight.
4.2.2 Configuration B, knotted.
2. Referenced Documents
2.1 ASTM Standards:
D 76 Specifications for Tensile Testing Machines for Textiles2
D 123 Terminology Relating to Textiles2
D 578 Specification for Glass Fiber Yarns2
D 885 Test Methods for Tire Cords, Tire Cord Fabrics, and
Industrial Filament Yarns Made from Manufactured
Organic-Base Fibers2
1
This test method is under the jurisdiction of ASTM Committee D13 on Textiles
and is the direct responsibility of Subcommittee D13.58 on Yarn Test Methods,
General.
Current edition approved Sept. 10, 2002. Published November 2002. Originally
published as D 2256 – 64 T. Last previous edition D 2256 – 97.
2
Annual Book of ASTM Standards, Vol 07.01.
3
4
Annual Book of ASTM Standards, Vol 07.02.
Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1
D 2256 – 02
necessary for a given yarn depending upon its structure and
composition. To prevent slippage in the clamps or damage as a
result of being gripped in the clamps, special clamping
adaptations may be necessary with high modulus yarns made
from fibers such as glass or aramid or extended chain polyolefin. Specimen clamping may be modified as required at the
discretion of the individual laboratory providing a representative force-elongation curve is obtained. In any event, the
procedure described in this test method for obtaining tensile
properties must be maintained.
5.5 Breaking Strength—The breaking strength of a yarn
influences the breaking strength of fabrics made from the yarn,
although the breaking strength of a fabric also depends on its
construction and may be affected by manufacturing operations.
5.5.1 Because breaking strength for any fiber-type is approximately proportional to linear density, strands of different
sizes can be compared by converting the observed breaking
strength to breaking tenacity (centinewtons per tex, gramsforce per tex, or grams-force per denier).
5.6 Elongation—The elongation of a yarn has an influence
on the manufacturing process and the products made. It
provides an indication of the likely stretch behavior of garment
areas such as knees, elbows, or other points of stress. It also
provides design criteria for stretch behavior of yarns or cords
used as reinforcement for items such as plastic products, hose,
and tires.
5.7 Force-Elongation Curve—Force-elongation curves permit the calculation of various values, not all of which are
discussed in this test method, such as elongation at break,
elongation at specified force, force at specified elongation,
initial elastic modulus which is resistance to stretching, compliance which is ability to yield under stress, and is the
reciprocal of the elastic modulus, and area under the curve, a
measure of toughness, which is proportional to the work done.
4.2.3 Configuration C, looped.
4.3 This test method also offers the following six conditions
of test with respect to moisture content of the specimens at the
time of testing:
4.3.1 Condition 1, conditioned to moisture equilibrium for
testing with standard atmosphere for testing textiles.
4.3.2 Condition 2, wet not immersed.
4.3.3 Condition 3, wet immersed.
4.3.4 Condition 4, oven-dried.
4.3.5 Condition 5, high temperature.
4.3.6 Condition 6, low temperature.
4.4 A test option is specified by combining a specimen
configuration and a moisture content condition, for example,
Option A1 means a straight specimen conditioned and tested in
a standard atmosphere for testing textiles.
4.5 Unless otherwise indicated, the phrase “single-strand
breaking force” is associated with Option A1.
5. Significance and Use
5.1 Acceptance Testing—Option A1 of Test Method D 2256
is considered satisfactory for acceptance testing of commercial
shipments because the test method has been used extensively in
the trade for acceptance testing. However, this statement is not
applicable to knot and loop breaking force tests, tests on wet
specimens, tests on oven-dried specimens, or tests on specimens exposed to low or high temperatures and should be used
with caution for acceptance testing because factual information
on between-laboratory precision and bias is not available.
5.1.1 If there are differences of practical significance between reported test results for two laboratories (or more),
comparative tests should be performed to determine if there is
a statistical bias between them, using competent statistical
assistance. As a minimum, use the samples for such a comparative tests that are as homogeneous as possible, drawn from
the same lot of material as the samples that resulted in disparate
results during initial testing and randomly assigned in equal
numbers to each laboratory. The test results from the laboratories involved should be compared using a statistical test for
unpaired data, a probability level chosen prior to the testing
series. If a bias is found, either its cause must be found and
corrected, or future test results for that material must be
adjusted in consideration of the known bias.
5.2 Fundamental Properties—The breaking tenacity, calculated from the breaking force and the linear density, and the
elongation are fundamental properties that are widely used to
establish limitations on yarn processing or conversion and on
their end-use applications. Initial modulus is a measure of the
resistance of the yarn to extension at forces below the yield
point. The chord modulus is used to estimate the resistance to
imposed strain. The breaking toughness is a measure of the
work necessary to break the yarn.
5.3 Comparison to Skein Testing—The single-strand
method gives a more accurate measure of breaking force
present in the material than does the skein method and uses less
material. The skein-breaking force is always lower than the
sum of the breaking forces of the same number of ends broken
individually.
5.4 Applicability—Most yarns can be tested by this test
method. Some modification of clamping techniques may be
NOTE 3—Force-elongation curves can be converted to stress-strain
curves if the force is converted to unit stress, such as to centinewtons per
tex, or pounds per square inch, or pascals, or grams-force per tex, or
grams-force per denier, and the elongation is based on change per unit
length.
5.8 Knot and Loop Breaking Force—The reduction in
breaking force due to the presence of a knot or loop is
considered a measure of the brittleness of the yarn. Elongation
in knot or loop tests is not known to have any significance and
is not usually reported.
5.9 Rate of Operation—In general, the breaking force
decreases slightly as time-to-break increases.
5.9.1 Operation of CRT, CRE, and CRL tension testing
machines at a constant time-to-break has been found to
minimize differences in test results between the three types of
tension testing machines. When tensile tests are performed at a
fixed time-to-break, then reasonable agreement in breaking
force has generally been found to exist between CRT and CRE
tension testing machines.5 Consistent results are also obtained
between different manufacturers of CRL tension testing machines when they are operated at the same time-to-break. The
5
Tweedie, A. S., Metton, M. T., and Fry, J. M., Textile Research Journal, Vol 29,
March 1959, pp. 235–251, and Tweedie, A. S., and Metton, M. T., Textile Research
Journal, Vol 29, March 1959, pp. 589–591.
2
D 2256 – 02
Automatic (self-loading and recording) single-end tension
testing machines may be used, provided they meet the requirements as to gage length, rate of operation, and accuracy of
calibration. The tension testing machine may be interfaced
with a computer system for operation and data gathering. The
CRE-type tension testing machine is recommended unless
otherwise agreed upon between the purchaser and the supplier.
agreement is not necessarily good, however, between CRE or
CRT tension testing machines on the one hand and CRL
tension testing machines on the other even when they are all
operated at the same time-to-break. The CRE-type tester is the
preferred tension testing machine.
5.9.2 This test method specifies an average time-to-break of
20 6 3 s as recommended by ISO TC 38 on Textiles, The
International Standards Association test committee for standardizing tests for fibers, yarns, and fabrics. It also provides for
alternate speeds, such as 300 6 10 mm (12 6 0.5 in.)/min
when using a 250-mm (10-in.) gage length. See 9.2.
5.9.3 The tolerance of 63 s for the time-to-break is wide
enough to permit convenient adjustment of the tension testing
machine’s rate of operation, and it is narrow enough to ensure
good agreement between tests. The difference in breaking force
between tests at 17 and 23 s will usually not exceed 1.5 % of
the higher value.
5.9.4 In case a tension testing machine is not capable of
being operated at 20-s time-to-break, alternative rates of
operation are included in this test method. These alternative
rates may be used only by agreement between the parties
concerned or when required in an applicable material specification.
5.10 Tests on Wet Specimens—Tests on wet specimens are
usually made only on yarns which show a loss of breaking
force when wet or when exposed to high humidity, for
example, yarns made from animal fibers and man-made fibers
based on regenerated and modified cellulose. Wet tests are
made on flax yarns to detect adulteration by failure to show a
gain in breaking force.
5.11 Tests on Oven-Dried Specimens and Specimens at High
Temperatures—Tests on oven-dried specimens at standard or
high temperatures are usually made only on yarns that will be
used at high temperatures or will be used under very dry
conditions which will affect the observed breaking force, for
example, on rayon yarns intended for use in tire cords and
yarns for other industrial purposes. Note that results obtained
when testing oven-dried specimens at standard temperature
will not necessarily agree with the results obtained when
testing oven-dried yarns at high temperatures.
5.12 Tests on Specimens at Low Temperatures—Tests on
specimens exposed to low temperatures are usually made only
on yarns that will be used at low temperatures, for example,
yarns used in outerwear designed for cold climates or outerspace situations. Low-temperature tests are made on coated
yarns used in the manufacture of materials used in outdoor
applications, such as screening fabrics.
NOTE 4—Test machines capable of both tension and compression are
acceptable for use with Test Method D 2256 when operated in the tension
mode.
NOTE 5—Flat-faced clamps are usually used with fine yarns. The
snubbing-type clamps are used with coarse yarns or yarns that show a high
breaking force. They are also used when specimens slip in the clamps or
the number of breaks at or close to the jaws exceeds statistical expectations. To check slippage, make a mark on the specimen as close as possible
to the back of each clamp, operate the machine to break the specimen, and
observe whether the marks have moved from the jaw faces of either
clamp.
6.1.1 Recorders on tension testing machines must have
adequate pen response to properly record the force-elongation
curve as specified in Specification D 76.
6.2 Tank, that can be fitted to the tension testing machine
and used to test specimens while immersed in water.
6.3 Container, separate from the testing machine for wetting out specimens to be tested without immersion.
6.4 Area-Measuring Device—An integrating accessory to
the tension testing machine or a planimeter.
6.5 Distilled or Deionized Water and Nonionic Wetting
Agent, for wet specimens only.
6.6 Conditioning Rack and Umbrella Reel (or Holder), on
which specimens, cut to convenient length, may be clamped
and from which they may be taken one at a time without loss
of twist.
6.7 Peg or Spindle, on which the package may be mounted
to rotate freely as specimens are taken (for samples on bobbins,
spools, tubes, etc.).
6.8 Holder, on which the yarn may be supported without
tension and without loss of twist while in the water (for wet
specimens only).
6.9 Oven and Specimen Holders, described in Methods
D 885 (for oven-dried specimens only).
6.10 Oven, that can be fitted to the tension testing machine
and used to test specimens while exposed to elevated temperatures, as specified by an applicable order or contract. See Note
6.
6.11 Cold Chamber, that can be fitted to the tension testing
machine and used to test specimens while exposed to low
temperatures, such as − 40°C (−40°F) as specified by an
applicable order or contract. See Note 6.
6. Apparatus and Reagents
6.1 Tension Testing Machine, of the CRE, CRL, or CRT
type, conforming to Specification D 76, with respect to force
indication, working range, capacity, and verification of recorded elongation, and designed for operation at the rates
specified in 9.1. A variable-speed drive, a change of gears, or
interchangeable weights are required to obtain the 20-s timeto-break. If the rate of operation is adjusted in steps, the steps
should be no greater than 1.25:1.00. The tension testing
machine may be equipped with: (1) clamps having flat-faced
jaws or (2) capstan-, drum-, or snubbing-type clamps (Note 5).
NOTE 6—Units described in 6.10 and 6.11 can be obtained as a
single-unit environmental chamber capable of exposing yarns to both low
and elevated temperatures.
7. Sampling
7.1 Lot Sample—As a lot sample for acceptance testing,
take at random the number of shipping units directed in an
applicable material specification or other agreement between
the purchaser and the supplier, such as an agreement to use
Practice D 2258. Consider shipping cases or other shipping
3
D 2256 – 02
or by agreement 500 6 5 mm (20 6 0.2 in.), from nip to nip
of the clamps along the specimen axis (including any portion in
contact with snubbing surfaces).
9.3.1 For Conditions 2, 4, 5, and 6, using tension testing
machines with an equipped water tank, oven, or cold chamber,
the pulling mechanism may require repositioning to allow for
shrinkage or stretch. When elongation is measured, the change
in the gage length must be considered in the calculation. When
shrinkage interferes with determination of elongation measurements; cooling of the test chamber may be required between
subsequent loading of individual specimens.
units to be the primary sampling units.
NOTE 7—An adequate specification or other agreement between the
purchaser and the supplier requires taking into account the variability
between shipping units, between packages or ends within a shipping unit,
and between specimens from a single package so as to provide a sampling
plan with a meaningful producer’s risk, consumer’s risk, acceptable
quality level, and limiting quality level.
7.2 Laboratory Sample—As a laboratory sample for acceptance testing, take at random from each shipping unit in the lot
sample the number of packages or ends directed in an
applicable material specification or other agreement between
the purchaser and the supplier such as an agreement to use
Practice D 2258. Preferably, the same number of packages
should be taken from each shipping unit in the lot sample. If
differing numbers of packages are to be taken from shipping
units in the lot sample, determine at random which shipping
units are to have each number of packages drawn.
7.3 Test Specimens—From each package in the laboratory
sample, take three specimens. When packages other than
beams contain more than one parallel wound end, select one
end from which to prepare the three specimens. For beams,
take three specimens from each end in the laboratory sample.
10. Configurations of Test Specimens
10.1 Configuration A, Straight Specimen—Handle specimens in a manner to avoid any change in twist or any stretching
of the specimen, or both (Note 8). Secure one end of the
specimen in one of the clamps of the tension testing machine.
Place the other end in the other clamp, applying 5 6 0.1 cN/tex
(0.5 gf/tex) pre-tension which is considered satisfactory to
remove any slack or kinks from most yarns without appreciable
stretching. Close the second clamp. Avoid touching the portion
of the specimen between the clamps with bare hands.
NOTE 8—Because of the difficulty of securing the same tension in all
the filaments and because of slippage in the clamps, erratic results are
frequently obtained with zero-twist multifilament yarns unless a small
amount of twist is inserted before testing. A twist of 14 6 1 tpcm/ =T (36
6 3 tpi/ =T ) or 43 6 4 tpcm/ =D (110 6 10 tpi/ =D ) where T equals
yarn number in tex and D equals yarn number in denier, is usually
satisfactory. But, for unfamiliar materials it may be necessary to test with
several different twist levels and determine the maximum breaking force.
Twist a test specimen length that is about 225 mm (9 in.) longer than the
gage length.
8. Conditioning of Specimens
8.1 Precondition and condition test specimens as directed in
Section 11 for each applicable test option and condition of test
as determined by an applicable purchase order or contract.
8.1.1 Avoid any change in twist or stretching of the yarn, or
both, during handling.
PROCEDURE
10.2 Configuration B, Knot-Breaking Force—Handle specimens in a manner to avoid any change in twist or any stretching
of the specimen, or both (Note 8). Place one end of the
specimen in one clamp of the machine, tie a single overhand
knot near the middle of the specimen, place the other end in the
second clamp, and tighten the clamp. Take care that the knot is
always tied in the direction specified (see Annex A1), as the
breaking force may be different depending on whether the knot
is made with or against the direction of twist.
10.2.1 For Configuration B, Conditions 2, 3, 4, 5, and 6, tie
loose knots in specimens before water or temperature exposure
to avoid handling between exposure and testing.
10.3 Configuration C, Loop-Breaking Force—Handle
specimens in a manner to avoid any change in twist or any
stretching of the specimen, or both (Note 8). Each specimen
consists of two pieces of yarn taken from one package or end.
Secure both ends of one piece in one clamp of the tension
testing machine without a change in twist having the length of
the loop about one half the gage length. Pass one end of the
second piece through the loop formed by the first, place both
ends of the second piece in the other clamp of the machine, and
close the clamp.
10.3.1 For Configuration C, Conditions 2, 3, 4, and 6,
prepare the looped specimens before water or temperature
exposure to avoid handling between exposure and testing.
9. Rate of Operation and Gage Length
9.1 Preferred Rate of Operation—Operate all tension testing machines at a rate to reach the breaking force in an average
time of 20 6 3 s from the start of the test. Break one or more
trial specimens, observe the time-to-break, and adjust the rate
of crosshead displacement if necessary.
9.2 Alternative Rates of Operation—In case the tension
testing machine is not capable of operating as specified in 9.1,
select a rate that will reach the breaking force in an average
time as close to 20 s as possible and report the average time to
break. For CRL tension testing machines, the rate of force
application per minute should be approximately three times the
breaking force, and for CRE tension testing machines the rate
of extension per minute should be approximately three times
the elongation at break. On CRT tension testing machines with
interchangeable or adjustable pendulum weights, the lower
capacity ranges result in longer times to break, and higher
capacities result in shorter times. These approximate rates are
not acceptable for referee testing where a time to break of 20
6 3 s is specified.
9.2.1 By agreement, or if required by material specifications, other operating rates may be used, for example, adjusting
the rate to 1206 5 % of the gage length per minute, that is, 300
6 10 mm/min (12 6 0.5 in./min) for 250-mm (10-in.) gage
lengths on CRT and CRE tension testing machines.
9.3 Gage Length—Adjust the tension testing machine in the
starting position to a distance of 250 6 3 mm (10 6 0.1 in.),
11. Testing Conditions
11.1 Condition 1, Ambient Air—Reel a short skein from
4
D 2256 – 02
specimens as directed in the oven-dried breaking force
(strength) procedure in Methods D 885. Remove a specimen
from the container and immediately mount the oven-dried
specimen in the tension testing machine in the normal setup.
Testing must begin within 20 6 2 s after removal of the
specimen from the container or discard the specimen and take
a new one.
11.5 Condition 5, at High Temperatures—Position the oven
in the tension testing machine to expose the entire specimen.
Preheat the oven until equilibrium is reached at the specified
temperature. Mount the specimen in the tension testing machine in the normal setup. Set the oven for the specified time at
the specified temperature as determined by an applicable order
or contract. The specimens are exposed for the specified time
and tested while at the specified temperature (see 9.3.1).
11.6 Condition 6, at Low Temperatures—Position the cold
chamber in the tension testing machine to expose the entire
specimen. Mount the specimen in the tension testing machine
in the normal setup. Set the cold chamber for the specified time
at the specified temperature as determined by an applicable
order contract. The specimens are exposed for the specified
time and tested while at the specified temperature (see 9.3.1).
each of the packages forming the laboratory sample. Precondition the skeins as directed in Practice D 1776 by bringing the
material into approximate moisture equilibrium with an atmosphere having a relative humidity between 5 and 25 % at a
temperature no higher than 50°C (120°F). After preconditioning, bring the sample skeins to moisture equilibrium for testing
in the standard atmosphere for testing textiles. Equilibrium is
considered to have been reached when two successive weighings not less than 15 min apart do not differ by more than 0.1 %
of the weight of the yarn.
NOTE 9—Conditioning in skein form is much more rapid than conditioning of tightly wound packages and is needed whenever other tests are
to be made on the same sample, that is, tests requiring a large amount of
conditioned material. However, the outer layers of a tight package reach
approximate equilibrium in a reasonable length of time; and where only a
few yards are to be used and extreme accuracy is not required (as, for
example, in production control work) it may be more convenient to
condition the yarn in package form.
NOTE 10—It is recognized that in practice yarns are frequently not
weighed to determine when moisture equilibrium has been reached. While
such a procedure cannot be accepted in cases of dispute, it may be
sufficient in routine testing to expose the material to the standard
atmosphere for testing for a reasonable period of time before the
specimens are tested. A time of at least 24 h has been found acceptable in
most cases. However, certain fibers may exhibit slow moisture equalization rates from the “as received” in shipment condition. When this is
known, a preconditioning cycle, as described in Practice D 1776 may be
agreed upon between contractual parties.
12. Measurement of Tensile Properties
12.1 Start the tension testing machine and the area integrator, if used, and continue running the test to rupture. Stop the
machine and reset to the initial gage position. Record the test
results to three significant figures.
12.2 If a specimen slips in the jaws, breaks at the edge of or
in the jaws, or if for any reason attributed to faulty operation
the result falls 20 % below the average of the breaking force
for the set of specimens, discard the result and test another
specimen. Continue until the required number of acceptable
breaks have been obtained.
12.2.1 The decision to discard the results of a break shall be
based on observation of the specimen during the test and upon
the inherent variability of the yarn. In the absence of other
criteria for rejecting a so-called jaw break, any break occurring
within 3 mm (1⁄8 in.) of the jaws which results in a value below
20 % of the average of the breaking force of all the other
breaks shall be discarded. No other break shall be discarded
unless the test is known to be faulty. It is difficult to determine
the precise reason for certain specimens breaking near the edge
of the jaws. If a jaw break is caused by damage to the specimen
by the jaws, then the results should be discarded. If, however,
it is merely due to randomly distributed weak places, it is a
perfectly legitimate result. Refer to Practice E 178 for treatment of outlying data points.
12.2.2 If a yarn manifests any slippage in the jaws or if more
than 24 % of the specimens break at a point within 3 mm (1⁄8
in.) of the edge of the jaw, then (1) the jaws may be padded, (2)
the yarn may be coated under the jaw face area, or (3) the
surface of the jaw face may be modified. If any of these
modifications are used, state the method of modification in the
report.
12.3 For instructions regarding the preparation of specimens
made from glass fiber to minimize damage in the jaws, see
Specification D 578.
12.4 Measure the elongation of the yarn to three significant
11.1.1 Mount the specimen directly in the tension testing
machine and test in the standard atmosphere for testing textiles,
which is 216 1°C (70 6 2°F) and 65 6 2 % relative humidity.
11.2 Condition 2, Wet Specimens Not Immersed on Tension
Testing Machine—Without disturbing twist, place the specimen on a holder and submerge in distilled or deionized water
at room temperature until thoroughly soaked (see 11.2.1).
Remove the specimen from the water and immediately mount
it in the tension testing machine in the normal setup. If more
than 60 s elapse between taking the wet specimen from the
water bath and starting a tension testing machine without a
tank, discard the specimen and take another.
11.2.1 The time of immersion must be sufficient to wet out
the specimens thoroughly, as indicated by no significant further
change in breaking force or elongation following longer
periods of immersion. This time period will be at least 2 min
for regenerated cellulose yarns and at least 10 min for acetate.
For yarns not readily wet out with water, such as those treated
with water-repellent or water-resistant materials, add a 0.1 %
solution of a nonionic wetting agent to the water bath. Do not
use any agent that will affect the physical properties of the yarn
appreciably. When wet modulus is to be determined, some fiber
types may require at least 24 h of immersion prior to testing.
11.3 Condition 3, Wet Specimens Immersed on Tension
Testing Machine—Mount the dry specimen in the tension
testing machine in the normal setup. Bring the water-bath tank
in position to immerse the entire specimen (see 9.3.1). Soak the
specimen in the water as described in 11.2.1 (Note 11).
NOTE 11—To minimize testing time, specimens may be wet-out in a
separate container, then transferred immediately upon removal from the
water bath to the tension testing machine equipped with a water-bath tank.
11.4 Condition 4, Oven-Dried Specimens—Oven-dry the
5
D 2256 – 02
Likewise, label a second point, P1 at a specified elongation,
such as 0 % elongation. Draw a straight line (secant) through
Points P1 and P2 intersecting the zero force axis. Other
elongation values may be used, for example, when provided for
in an applicable material specification. Calculate chord modulus using Eq 4. (See Appendix X2 and Fig. X2.1.)
figures at any stated force by means of a suitable recording
device at the same time as the breaking force is determined
unless otherwise agreed upon, as provided for in an applicable
material specification.
CALCULATIONS
Jch 5 ~F 3 100!/~ep 3 T!
13. Breaking Force
13.1 Record the breaking force of individual specimens;
that is, the maximum force to cause a specimen to rupture as
read directly from the tension testing machine expressed in
Newtons (pounds force) N (lbf).
where:
Jch = chord modulus between specified elongations, cN/
tex (gf/den, lbf/den),
F
= determined force on the constructed line, cN (gf,
lbf),
= corresponding elongation with respect to the conep
structed line and determined force, %, and
T
= linear density, tex (denier).
14. Breaking Tenacity
14.1 Calculate the breaking tenacity of individual specimens using Eq 1, as follows:
B 5 F/T
(4)
(1)
18. Breaking Toughness
where:
B = breaking tenacity, cN (gf, lbf) per tex or cN (gf, lbf)
per denier,
F = breaking force, CN (gf, lbf), and
T = linear density, tex (denier).
18.1 When using the force-elongation curves, draw a line
from the point of maximum force of each specimen perpendicular to the elongation axis. Measure the area bounded by the
curve, the perpendicular and the elongation axis by means of
an integrator or a planimeter, or cut out the area of the chart
under the force-elongation curve, weigh it, and calculate the
area under the curve using the weight of the unit area.
18.2 When determining the breaking toughness of yarns that
exhibit take-up of slack caused by crimp or design, the area
under the force-elongation curve which precedes the initial
modulus line represents the work to remove this slack. Automatic area measuring equipment may or may not include this
area in measuring breaking toughness, and therefore, such
information should be reported along with the value observed
for the breaking toughness.
18.3 Calculate the breaking toughness for each specimen
when using XY-type recorders using Eq 5, or when using
automatic area measuring equipment using Eq 6, as follows:
15. Elongation
15.1 Calculate the elongation of individual specimens from
XY-type recorders using Eq 2, as follows:
ep 5 ~E 3 R 3 100!/~C 3 Lg!
(2)
where:
ep = elongation percent,
E
= distance along the zero force axis from the point
corresponding to the point where the forceelongation curve passes the pre-tension force to a
point of corresponding force, mm (in.),
R
= testing speed rate, mm/min (in./min),
C = recording chart speed, mm/min (in./min), and
Lg = nominal gage length, mm (in.)
16. Initial Modulus
16.1 Locate the maximum slope and draw a line tangent to
the force-elongation curve between the tangent point for this
tangent line and the proportional elastic limit and through the
zero force axis. Measure the force and the corresponding
elongation with respect to the force axis. Calculate initial
modulus using Eq 3. (See Appendix X1 and Fig. X1.1 and Fig.
X1.2.)
Jo 5 ~F 3 100!/~ep 3 T!
Tu 5 ~Ac 3 S 3 R!/~Wc 3 C 3 T 3 L!
(5)
Tu 5 ~V 3 S 3 R!/~Ic 3 T 3 L!
(6)
where:
Tu
= breaking toughness, J/g (gf·cm/den cm, in. lbf/den
cm),
Ac = area under the force-elongation curve, cm2(in.2),
S
= full-scale force range, cN (gf, lbf),
R
= testing speed rate, cm/min (in./min),
Wc = recording chart width, cm (in.),
C
= recording chart speed, cm/min (in./min),
T
= linear density, tex or denier,
L
= nominal gage length of specimen, cm (in.),
V
= integrator reading, and
= integrator constant, per minute, determined as diIc
rected by the manufacturer.
(3)
where:
Jo = initial modulus, cN/tex (gf/den),
F = determined force on the drawn tangent line, cN (gf,
lbf),
ep = corresponding elongation with respect to the drawn
tangent line and determined force, %, and
T = linear density, tex (denier).
19. Average Values
19.1 Calculate the average values for breaking force, elongation, initial modulus, chord modulus, and breaking toughness of the observations for the individual specimens tested to
three significant figures.
17. Chord Modulus
17.1 Determine the force for a specified elongation, such as
10 %, and label that point on the force-elongation curve as P2.
6
D 2256 – 02
20.2.10 Make and model of tension testing machine.
20.2.11 Type of clamps used.
20.2.12 Type of padding used in jaws, modification of
specimens gripped in the jaws, or modification of jaw faces, if
used.
20.2.13 Full-scale force range used for testing.
REPORT, PRECISION AND BIAS, AND INDEXING
20. Report
20.1 Report that the specimens were tested as directed in
Test Method D 2256. Describe the material or product sampled
and the method of sampling used.
20.2 Report all of the following applicable items:
20.2.1 Average breaking force in N, gf, or lbf.
20.2.2 Average breaking tenacity or tenacity at a specified
elongation in cN/tex, cN/den, gf/tex, gf/den, or lbf/den.
20.2.3 Average elongation at specified force in percent.
20.2.4 Test option and condition used.
20.2.5 If requested, the average initial or chord modulus in
cN/tex, gf/den, or lbf/den. For chord modulus, state that portion
of the force-elongation curve used to determine the modulus,
such as, 0 to 10 % elongation, reported as 10 % chord modulus.
Other portions of the force-elongation curve can be reported as
requested.
20.2.6 If requested, the average breaking toughness in
joules/g (gf·cm/den cm, in. lbf/den cm).
20.2.7 If calculated, the standard deviation, coefficient of
variation, or both, of any of the properties.
20.2.8 If requested, include a force-elongation curve as part
of the report.
20.2.9 Number of specimens tested.
21. Precision and Bias
21.1 Interlaboratory Test Data—An interlaboratory test was
run in 1992 through 1994 in which randomly-drawn samples of
four materials were tested in each of the number of laboratories
as shown below. Two operators in respective laboratories each
tested ten specimens of each material using 3 different criteria:
(1) manual test machine with 10-in. gage and testing speed of
10 in./min, (2) manual test machine with 10-in. gage and break
criterion of 20 6 3 s, and (3) automatic test machine with a
break criterion of 5 6 1 s. Analysis of the data was conducted
using Practices D 2904 and D 2906. The components of
variance for breaking strength and elongation at break expressed as standard deviations were calculated to be the values
listed in Table 1 for respective test criteria. The four classes of
fibers, test criteria, and number of participating laboratories
were:
TABLE 1 Components of Variance Expressed as Standard DeviationsA
Single Material Comparison
Name of Property
Name of Product
Test Type
Breaking Strength, lbB
Nylon, 7.8 tex (70 denier)
Manual, 10 ipm, 10 in. gage
Manual, 20 6 3 s
Automatic, 5 6 1 s
Polyester, 150/34
Manual, 10 ipm, 10 in. gage
Manual, 20 6 3 s
Automatic, 5 6 1 s
Cotton, 32/1
Manual, 10 ipm, 10 in. gage
Manual, 20 6 3 s
Automatic, 5 6 1 s
Glass, 66 tex (600 denier)
Manual, 10 ipm, 10 in. gage
Manual, 20 6 3 s
Automatic, 5 6 1 s
Elongation at break, %
Nylon, 7.8 tex (70 Denier)
Manual, 10 ipm, 10 in. gage
Manual, 20 6 3 s
Automatic, 5 6 1 s
Polyester, 150/34
Manual, 10 ipm, 10 in. gage
Manual, 20 6 3 s
Automatic, 5 6 1 s
Cotton, 32/1
Manual, 10 ipm, 10 in. gage
Manual, 20 6 3 s
Automatic, 5 6 1 s
Glass, 66 tex (600 denier)
Manual, 10 ipm, 10 in. gage
Manual, 20 6 3 s
Automatic, 5 6 1 s
Standard Deviation, Units of Measure
Grand Average
No. of Tests per
Package
Single-Operator
Component
Within Laboratory
Component
Between Laboratory Component
0.52
0.55
0.56
10
10
10
0.040
0.364
0.038
0.013
0.006
0.012
0.031
0.054
0.019
1.25
1.28
1.26
10
10
10
0.060
0.089
0.041
0.000
0.034
0.000
0.073
0.070
0.049
0.57
0.56
0.59
10
10
10
0.060
0.065
0.062
0.000
0.000
0.013
0.068
0.066
0.031
7.23
8.53
8.02
10
10
10
0.748
0.481
0.650
0.297
0.219
0.000
1.450
0.926
0.631
55.70
55.30
59.70
10
10
10
5.187
3.210
3.044
0.677
1.333
0.000
10.928
12.966
5.222
29.30
32.30
33.20
10
10
10
3.626
3.343
2.162
0.000
0.000
0.000
8.359
8.440
4.615
6.31
6.16
6.39
10
10
10
0.551
0.515
0.477
0.203
0.063
0.454
1.068
1.209
0.234
2.23
2.50
2.37
10
10
10
0.456
0.146
0.196
0.157
0.091
0.000
0.588
0.402
0.202
A
The square roots of the components of variance are being reported to express the variability in the appropriate units of measure rather than as the square of those
units of measure.
B
The tests were conducted in U.S. Customary units and are expressed in pounds. Multiply pounds by 454 for gram units and pounds by 444.8 for a N units.
7
D 2256 – 02
Material
taken by the same well-trained operator using the same piece of
equipment and specimens drawn randomly from the sample of
material. Larger differences likely are to occur under all other
circumstances.
21.3 Precision—For the components of variance reported in
Table 1, two averages of observed values should be considered
significantly different at the 95 % probability level if the
difference equals or exceeds the critical differences listed in
Table 2 and Table 3, for breaking strength and elongation to
break, respectively.
Test Criteria Number (Number of
Participating Laboratories)
7.8 tex (70 denier) nylon
150/34 polyester
32/1 cotton
66 tex (600 denier) glass
1
1
1
1
(4)
(5)
(5)
(3)
2
2
2
2
(5)
(5)
(5)
(4)
3
3
3
3
(6)
(6)
(6)
(5)
21.2 Summary—In comparing two averages, the differences
should not exceed the single-operator precision values shown
in Table 2 and Table 3 for the respective number of tests and for
materials having averages similar to those shown in Table 2
and Table 3 in 95 out of 100 cases when all the observations are
TABLE 2 Critical Differences, for Conditions as NotedA
Single Material Comparison, Units as Indicated
Name of Property
Name of Product
Test Type
Breaking Strength, lbB
Nylon, 7.8 tex (70 Denier)
Manual, 10 ipm, 10 in. gage
Manual, 20 6 3 s
Automatic, 5 6 1 s
Polyester, 150/34
Manual, 10 ipm, 10 in. gage
Manual, 20 6 3 s
Automatic, 5 6 1 s
Cotton, 32/1
Manual, 10 ipm, 10 in. gage
Manual, 20 6 3 s
Automatic, 5 6 1 s
Glass, 66 tex (600 denier)
Manual, 10 ipm, 10 in. gage
Manual, 20 6 3 s
Automatic, 5 6 1 s
A
B
No. of Tests in
Each Average
Single-Operator
Precision
Within-Laboratory
Precision
Between-Laboratory
Precision
1
2
5
10
1
2
5
10
1
2
5
10
0.11
0.08
0.05
0.03
0.10
0.07
0.05
0.03
0.10
0.07
0.05
0.03
0.12
0.09
0.06
0.05
0.10
0.07
0.05
0.04
0.11
0.08
0.06
0.05
0.14
0.12
0.10
0.10
0.18
0.17
0.16
0.16
0.12
0.10
0.08
0.07
1
2
5
10
1
2
5
10
1
2
5
10
0.16
0.12
0.07
0.05
0.25
0.17
0.11
0.08
0.11
0.08
0.05
0.04
0.16
0.12
0.07
0.05
0.26
0.20
0.15
0.12
0.11
0.08
0.05
0.04
0.26
0.23
0.22
0.21
0.33
0.28
0.24
0.23
0.18
0.16
0.14
0.14
1
2
5
10
1
2
5
10
1
2
5
10
0.17
0.12
0.07
0.05
0.18
0.13
0.08
0.06
0.17
0.12
0.08
0.05
0.17
0.12
0.07
0.05
0.18
0.13
0.08
0.06
0.18
0.13
0.09
0.07
0.25
0.22
0.20
0.19
0.26
0.22
0.20
0.19
0.20
0.15
0.12
0.11
1
2
5
10
1
2
5
10
1
2
5
10
2.07
1.47
0.95
0.67
1.34
0.95
0.60
0.42
1.80
1.30
0.76
0.57
2.23
1.68
1.24
1.05
1.47
1.13
0.85
0.74
1.80
1.27
0.76
0.57
4.59
4.35
4.20
4.15
2.96
2.80
2.71
2.67
2.51
2.16
3.54
1.84
The critical differences were calculated using t = 1.960, which is based on infinite df.
See Table 1, Note B.
8
D 2256 – 02
TABLE 3 Critical Differences, for Conditions as NotedA
Single Material Comparison, Units as Indicated
Name of Property
Name of Product
Test Type
Elongation at Break, %
Nylon, 7.8 tex (70 Denier)
Manual, 10 ipm. 10 in. gage
Manual, 20 6 3 s
Automatic, 5 6 1 s
Polyester, 150/34
Manual, 10 ipm, 10 in. gage
Manual, 20 6 3 s
Automatic, 5 6 1 s
Cotton, 32/1
Manual, 10 ipm, 10 in. gage
Manual, 20 6 3 s
Automatic, 5 6 1 s
Glass, 66 tex (600 denier)
Manual, 10 ipm, 10 in. gage
Manual, 20 6 3 s
Automatic, 5 6 1 s
A
No. of Tests in
Each Average
Single-Operator
Precision
Within-Laboratory
Precision
Between-Laboratory
Precision
1
2
5
10
1
2
5
10
1
2
5
10
14.38
10.17
6.43
4.55
8.90
6.29
3.98
2.81
8.44
5.97
3.77
2.67
14.50
10.34
6.70
4.92
9.63
7.30
5.43
4.64
8.44
5.97
3.77
2.67
33.58
32.00
31.02
30.68
37.20
36.67
36.34
36.23
16.75
15.65
14.96
14.72
1
2
5
10
1
2
5
10
1
2
5
10
10.05
7.10
4.49
3.18
9.26
6.55
4.14
2.93
5.99
4.24
2.68
1.89
10.05
7.10
4.49
3.18
9.26
6.56
4.14
2.93
5.99
4.24
2.68
1.89
25.25
24.23
23.60
23.38
25.16
24.29
23.75
23.57
14.12
13.47
13.07
12.93
1
2
5
10
1
2
5
10
1
2
5
10
1.53
1.08
0.68
0.48
1.43
1.01
0.68
0.48
1.32
0.93
0.59
0.42
1.63
1.22
0.88
0.74
1.44
1.02
0.88
0.74
1.82
1.57
1.39
1.33
3.38
3.20
3.09
3.05
3.65
3.50
3.09
3.05
1.94
1.70
1.53
1.48
1
2
5
10
1
2
5
10
1
2
5
10
1.26
0.89
0.57
0.40
0.40
0.29
0.18
0.13
0.54
0.38
0.27
0.17
1.34
0.99
0.71
0.59
0.48
0.88
0.31
0.28
0.54
0.38
0.27
0.17
2.11
1.90
1.78
1.73
1.21
1.18
1.16
1.15
0.78
0.68
0.62
0.59
The critical differences were calculated using t = 1.960, which is based on infinite df.
method. Within this limitation, the procedures in this test
method for measuring these properties have no known bias.
21.4.1 Interlaboratory testing indicated a bias between laboratories for modulus values related to the common selection of
the force-extension curve slope and differences between various software used to calculate the modulus values. Of those
laboratories reporting values representing the three test criteria
used in the interlaboratory test, the following range of values
were observed:
NOTE 12—The tabulated values of the critical differences should be
considered to be a general statement, particularly with respect to betweenlaboratory precision. Before a meaningful statement can be made about
two specific laboratories, the amount of statistical bias, if any, between
them must be established, with each comparison being based on recent
data obtained on specimens taken from a lot of material to the type being
evaluated so as to be as nearly homogeneous as possible, and then
randomly assigned in equal numbers to each of the laboratories.
NOTE 13—Since the interlaboratory test for the 70 denier nylon and the
600 denier glass used only four and three laboratories, respectively for the
manual test at a crosshead of 10 in./min, estimates should be used with
special caution.
Material
21.4 Bias—The values of the breaking strength and elongation at break only can be defined in terms of a specific test
7.8 tex (70 denier) nylon
150/34 polyester
9
Initial Modulus, Range of Values, gf/tex
148–183
214–856
D 2256 – 02
32/1 cotton
66 tex (600 denier) glass
material of the type being evaluated, so as to be as nearly
homogeneous as possible, and then randomly assigned in equal
numbers in each laboratory. See 5.1.1.
195–245
1017–2299
21.4.1.1 Before a meaningful statement can be made about
two specific laboratories performing modulus tests on yarns
using this test method, the amount of statistical bias, if any,
between them must be established with each comparison being
based on recent data obtained on specimens taken from a lot of
22. Keywords
22.1 breaking strength; elongation; yarns
ANNEX
(Mandatory Information)
A1. DIRECTION OF KNOTS
A1.1 Descriptive Terms Specific to Fig. A1.1 and Fig. A1.2:
A1.1.1 overhand knot—a simple single knot, tied in either
direction.
A1.1.2 bight—a bend or loop; the middle portion as distinguished from the ends. In Fig. A1.1 and Fig. A1.2, the bight lies
toward the bottom of the page.
A1.1.3 type “O” knot—one in which, when the bight is
below, the bight crosses over the right-hand end, as shown in
Fig. A1.1(b).
A1.1.4 type “U” knot—one in which, when the bight is
below, the bight crosses under the right-hand end as shown in
Fig. A1.2(b).
FIG. A1.2 Type “U” Knot
A1.2.1 Unless otherwise agreed, use the Type “O” knot for
Z twist yarns and Type “U” for S twist yarns. In plied yarns, the
last twist determines the type of knot to be used.
A1.3 Tying Knots:
A1.3.1 To tie the Type “O” knot, bend the right-hand end
downward and bring it up behind the left-hand end, as shown
in Fig. A1.1(a), then bring the right-hand end forward and pass
it through the bight from front to back.
A1.3.2 To tie the Type “U” knot, bend the right-hand end
downward and bring it up in front of the left-hand end, as
shown in Fig. A1.2(a); then bring the right-hand end forward
through the bight from behind.
A1.2 Choice of Knots:
FIG. A1.1 Type “O” Knot
APPENDIXES
(Nonmandatory Information)
X1. INITIAL MODULUS
X1.2 In the case of a yarn that does not exhibit any linear
region (Fig. X1.2), a tangent K8B8 is constructed to the
maximum slope and its extension intersecting the zero-force
axis at Point B8. This intersection point B8 is the zero point
from which strain is measured. Point C8, the point where line
K8B8 first touches the force-elongation curve, is the tangent
point.
X1.2.1 The initial modulus may be determined by dividing
the force at any point along line B8K8 (or its extension) by the
strain at the same point (measured from point B8, defined as
zero strain).
X1.1 In the case of a yarn exhibiting a region that obeys
Hooke’s law (Fig. X1.1), a continuation of the linear region of
the curve is constructed through the zero-force axis. This
intersection point B is the zero elongation point from which
strain is measured.
X1.1.1 The initial modulus can be determined by dividing
the force at any point along the line BD (or its extension) by the
strain at the same point (measured form Point B, defined as
zero strain). Point C, the point where line BD first touches the
force-elongation curve is the tangent point.
10
D 2256 – 02
FIG. X1.1 Material with Hookean Region
FIG. X1.2 Material with No Hookean Region
11
D 2256 – 02
X2. CHORD MODULUS
X2.1 In a typical force-elongation curve (Fig. X2.1), a
straight line is constructed through the zero force axis, such as
zero strain point A9 and a second point, such as 10 % strain,
point M9. The intersection point A9 is the zero elongation point
from which elongation is measured.
X2.1.1 The chord modulus may be determined by dividing
the force at any point along line A9M9 (or its extension) by the
elongation at the same point (measured from point A9, defined
as zero strain).
X2.1.2 Fig. X2.1 also represents a straight line constructed
through any two specified points, Point Q9 and Point R9, other
than zero and 10 % strain. In this case, the line extends through
the zero load axis at Point B9. This intersection is the zero
elongation point from which elongation is measured. The
chord modulus can be determined by dividing the force at any
point along Line Q9R9 (or its extension) by the elongation at
the same point (measured from Point B9, defined as zero
strain).
FIG. X2.1 Construction for Chord Modulus
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12